Katie is 5 feet tall. She casts a 3-foot long shadow at the same times that a flagpole casts an 18-foot long shadow. How tall is the flagpole?

Answer 1

use the ratio: shadow / height and assume it to be constant

katie : 3 ft / 5ft

tree : 18 ft / x

because the ratio is constant, they must equal each other : ( 3 / 5 ) = ( 18 / x ) solve for x

x = 18 / ( 3 /5 ) = (18 · 5) / 3

x = 30 feet

The tree is 30 feet tall.